This invention relates to a beverage brewing apparatus suitable for use in a beverage vending machine, and more particularly, to improvement of the sealing situation between the brewing liquid cylinder and piston during the brewing operation of the apparatus.
Beverage brewing apparatus suitable for use in vending machines for preparing single cup quantities of beverages from beverage material is well known in the prior art. For example, U.S. Pat. No. 3,349,690 issued to William Heier discloses one construction for such a brewing apparatus.
Referring to FIG. 1 on the application drawings, the basic construction and brewing cycle of a prior art apparatus will be described. Frame 1 of the apparatus supports a vertically movable open-bottom cylinder 2 which has the bottom opening covered by a filter member 3. A vertically movable piston 4 is disposed within cylinder 2 and relative movement between cylinder 2 and piston 4 is created by operation of a cam member 5 driven by motor 6. One end opening of a duct 7 is connected with a water tank (not shown) through electromagnetic valve 9, this end opening being closely placed above the upper opening of cylinder 2 to supply hot water into cylinder 2. A brewing cavity 10, which is generally reciprocable horizontally between a brewing position (this position being shown by solid lines in FIG. 1) and a rest position (this position being shown by dot and dash lines in FIG. 1), is placed beneath the cylinder 2 and sealed with the lower portion of cylinder 2 in the brewing position.
The prior art apparatus is also provided with a coffee hopper 11 which is connected with a canister 12 for receiving a charge of coffee. The ground coffee fills canister 12 which is provided with suitable feed means to deliver a predetermined quantity of fresh ground coffee into hopper 11 at a point prior to the start of the brew extracting operation.
In this apparatus, brewing cavity 10, at the start of a brewing cycle initiated by a coin operated switch for example, moves horizontally toward the brewing position from the rest position to a place beneath the bottom opening of cylinder 2. During this horizontal movement, the ground coffee is supplied into the brewing cavity 10 through coffee hopper 11 at a supply position (this position being indicated by dotted lines in FIG. 1). When brewing cavity 10 is properly aligned beneath the cylinder 2, due to the operation of cam member 5, cylinder 2 moves downwardly into tight engagement with cavity 10. This forms a chamber which is filled with hot water supplied through duct 7.
Thereafter, piston 4 moves downwardly to force the water through the filter member 3 into the ground coffee in cavity 10 and through an outlet conduct 13 to a cup 14 placed at a dispensing station. Before introducing coffee into the cup, the extracted coffee would be mixed with a suitable amount of sugar and/or cream, both of which are supplied from canisters 15 and 16, respectively. Thereafter, the brewing cavity 10 containing the spent coffee grounds is moved to its rest position and the grounds in the brewing cavity 10 are discarded at a position which is disposed just before the rest position is reached. When the brewing cavity 10 is returned to its rest position, one brewing cycle has been completed.
During the brewing cycle, particularly during the extracting operation, the sealing between the inner surface of cylinder 2 and outer peripheral surface of piston 4 should be very good to effect the most favorable extracting operation. Therefore, since piston 4 is slidably disposed within the cylinder and is provided with a sealing member, the piston 4 should be moved straight downwardly. However, movement of piston 4 is controlled by the operation of cam member 5 so a horizontal force component acts against piston 4 by the operation of cam member 5. Thus, it is possible that the axial center of piston 4 becomes offset from the center of cylinder 2 and as a result of this offset, sealing conditions between piston 4 and cylinder 2 become impaired.